Ted Cruz, who won the Republican caucus in Iowa on Monday, says he has always opposed legalizing the 11 million people who live in the U.S. without the government's permission. Donald Trump, who finished second in Iowa, has promised to deport them all, while Marco Rubio, who was a point behind Trump, has renounced the "path to citizenship" he used to support and wants to double the size of the U.S. Border Patrol, even as net migration from Mexico has dropped below zero.

On the face of it, the Republican Party is not in a very pro-immigrant mood. Yet the positions staked out by Cruz and Trump are unpopular even among Republicans and could prove fatal to a party that needs support from Hispanic voters to win.

In the race for the Republican presidential nomination, Trump remains the front-runner nationally, polling at or above 30 percent, and hostility to immigration is the most prominent theme of his campaign. The billionaire reality TV star, who has disparaged Mexican immigrants as criminals, rapists, and drug dealers, promises to end birthright citizenship, triple the number of Immigration and Customs Enforcement officers, "humanely" deport 11 million unauthorized immigrants, and build a wall on our southern border at the Mexican government's expense.

Cruz does not go quite as far as Trump, but he promises to "build a wall that works, triple border security, and put in place the surveillance and biometric tracking [required] to secure the border." The Texas senator wants to boost deportations and opposes anything even vaguely resembling "amnesty."

During last week's Republican presidential debate, Cruz slammed Rubio for getting elected to the Senate as an opponent of amnesty in 2010, then supporting a 2013 bill that would have allowed illegal immigrants who met certain conditions to become citizens. The Florida senator desperately tried to distance himself from that bill, saying "there's not going to be consensus on this issue until we enforce our immigration laws."

Cruz himself seemed to support some form of legalization in 2013, proposing what he described as a "middle ground" amendment to the immigration bill that would "allow for those 11 million people who are here illegally a legal status, with citizenship off the table." Cruz now claims the amendment was merely a ploy aimed at showing that Democrats were not interested in bringing unauthorized immigrants out of the shadows so much as boosting the number of voters inclined to support their party.

One reason immigrants like Democrats more than Republicans is that Democrats like immigrants more than Republicans do. According to polling by the Pew Research Center, Republicans are more likely than Democrats to say immigrants have a negative impact on crime, the economy, and society.

Yet Pew also finds that just a quarter of Republicans favor the mass deportation Trump promises, while most think "there should be a way for undocumented immigrants to remain in the country" -- something none of the leading Republican candidates is advocating. In the general population, Pew reports, just 17 percent of Americans want mass deportation, while 72 percent support legalization.

Results from the most recent Gallup poll are similar, with 79 percent of Americans supporting work permits or citizenship for unauthorized immigrants and just 19 percent favoring mass deportation. Gallup also found that almost two-thirds of Americans think immigration should be increased or kept at its current level.

The immigration policies favored by Trump and Cruz are especially unpopular among the growing bloc of Hispanic voters, and that poses a real problem for Republicans. Mitt Romney, who said he would encourage "self-deportation" by making economic conditions intolerable for unauthorized immigrants, won just 27 percent of the Hispanic vote in 2012, down from 44 percent for George W. Bush in 2004.

The polling firm Latino Decisions calculates that the 2016 Republican nominee will need at least 42 percent of the Hispanic vote to win the election. He will not get that by talking up border walls and deportations.